Backup v4 much slower than v3

System: windows 7 ultimate 64-bit
CB: 4.0.7

I run the CB from a perl script started as a scheduled job, that is NOT using the scheduling options of CB itself. Recently I changed from CB v3 to CB v4. The perl script was not modified. However, the full backup now takes 2.5 hours instaed of 1.5 hours. Funnily enough, the differential backup has slightly speeded up in v4.
The normal (full) backup is started as a scheduled job with process priority 5. The differentials are started with process priority 6. This has not changed going from v3 to v4.
Any change in how the /processorusage and /diskusage options are processed? It seems these are missing from the current command line options explanation. If they are not supported anymore and this is the cause of the longer run, I would love to have them backā€¦

No change was done for these. To achieve best speed make sure they are set to highest level possible.
You can also try to run a full backup with same settings from GUI (without scripts) to compare.

Thanks

No change was done for these. To achieve best speed make sure they are set to highest level possible. You can also try to run a full backup with same settings from GUI (without scripts) to compare.

Thanks. I did and I will. Could take a few days, though.

I ran CBU interactively. Speed was about the same as the scheduled job. Performance monitor showed CPU priority as high, I/O priority as normal (as it should be). I wonder if the number of I/O operations has increased (or saying the same thing in another way, the average size of an I/O request has diminished). I could not tell this time, because I had not loaded the diskperf driver. Next time I will do better, might again take a few days.